Serialize access to observed state

This should fix concurrent accesses to the map.

Signed-off-by: Mathieu Champlon <mathieu.champlon@docker.com>

pkg/compose/convergence.go

@@ -55,6 +55,19 @@ const (
 type convergence struct {
 	service       *composeService
 	observedState map[string]Containers
+	stateMutex    sync.Mutex
+}
+
+func (c *convergence) getObservedState(serviceName string) Containers {
+	c.stateMutex.Lock()
+	defer c.stateMutex.Unlock()
+	return c.observedState[serviceName]
+}
+
+func (c *convergence) setObservedState(serviceName string, containers Containers) {
+	c.stateMutex.Lock()
+	defer c.stateMutex.Unlock()
+	c.observedState[serviceName] = containers
 }
 
 func newConvergence(services []string, state Containers, s *composeService) *convergence {
@@ -97,7 +110,7 @@ var mu sync.Mutex
 
 // updateProject updates project after service converged, so dependent services relying on `service:xx` can refer to actual containers.
 func (c *convergence) updateProject(project *types.Project, service string) {
-	containers := c.observedState[service]
+	containers := c.getObservedState(service)
 	container := containers[0]
 
 	// operation is protected by a Mutex so that we can safely update project.Services while running concurrent convergence on services
@@ -148,7 +161,7 @@ func (c *convergence) ensureService(ctx context.Context, project *types.Project,
 	if err != nil {
 		return err
 	}
-	containers := c.observedState[service.Name]
+	containers := c.getObservedState(service.Name)
 	actual := len(containers)
 	updated := make(Containers, expected)
 
@@ -224,7 +237,7 @@ func (c *convergence) ensureService(ctx context.Context, project *types.Project,
 	}
 
 	err = eg.Wait()
-	c.observedState[service.Name] = updated
+	c.setObservedState(service.Name, updated)
 	return err
 }